This invention relates to a grinding machine and more particularly, to a grinding machine in which three cup-shaped grinding wheels are disposed in different heights spaced from each other by a distance corresponding to one third of the feed pitch of the work piece to be processed. The grinder engages the work piece in three directions at right angles thereto with the center axis of each wheel deviated from the axis of the work piece by the effective radius of the wheel (the distance from the center axis of the wheel to substantially one half of the wall thickness of the cup of the wheel) so that a substantial amount of the material can be removed from the work piece at one time.
In one prior art grinding machine for cutting work pieces into cylindrical products, a single cup-shaped grinding wheel is employed and as a result, the wheel removes only a small amount of the material from the work piece at one time. Therefore, the prior art grinding machine is quite inefficient in cutting a square cross-section work-piece into a cylindrical product or cutting work pieces which are not truly circular and have a substantial margin for cutting, such as ceramic and glass wares, into true circular products.